Image capture devices, such as digital video cameras or digital still cameras, are used in different applications and environments. An image capture device should be capable of producing high quality imagery under a variety of lighting conditions. For example, image capture devices should be capable of operating effectively in environments that include large amounts of reflected or saturated light, as well as in environments that include high levels of contrast. A typical image capture device performs automatic exposure to select an exposure value (EV) that achieves a certain target brightness for a scene. For example, an image capture device may select an EV that produces an image frame of the scene with an average brightness value equivalent to approximately 18% gray.
An automatic exposure process may adjust aperture size, shutter speed, and sensor gain of the image capture device to correspond to the selected EV. In this way, the automatic exposure process controls an amount of light that reaches a sensor array within the image capture device to produce an image frame of a scene at the target brightness. However, some scenes may require a higher average brightness value while other scenes may require a lower average brightness value. For example, a snow scene includes a large amount of reflected light, for which the automatic exposure process may overcompensate, causing the image frame to look unnaturally dark. On the other hand, a scene containing a white document next to a black laptop includes a high contrast level, for which the automatic exposure process may also overcompensate, causing the white document to appear highly saturated in the image frame.
Exposure compensation is common in digital still cameras, but may also be utilized in digital video cameras and other types of image capture devices. Some cameras may be configured to perform auto exposure relative to a pre-selected area or scene section to determine the proper exposure. However, such an approach may not identify the proper region of interest. Accordingly, in some cases, conventional auto exposure may encounter errors, for example, where the wrong region of interest is identified or when the scene is backlit. A backlit object may cause some auto-exposure processes to improperly set exposure for the object.